Oops, I was mentioned.

(10/02/2011 05:34 PM), Jeremy Kemper wrote:
>> |3. MVM, with inter-vm message passing.
>>
>> I have not decided yet, but since MVM requires incompatible changes to
>> C API, so we might pend it to Ruby 3.0.
> 
> I understand @shyouhei's branch is backward compatible for extensions
> that don't use MVM features.
> 
> I think it's another case where the benefits outweigh the cost.
> 
> C extensions can gradually update for MVM compatibility.
> 
> Otherwise, we wait for Ruby 3.0 and we confront the same problem. Then
> we pend it to Ruby 4.0 for the same reason, because it requires
> incompatible changes to the C API.

It seems the definition of "API" differs between you.

My branch is merely compatible in C source code layer.  That is, in
short, binary incompatible.  You have to recompile all the existing
extensions.  If you can accept this situation, yes, the source codes
themselves are compatible.